Vapor electric device



Sept; 22, 1953 R. J. BALLARD 2,653,266

VAPOR ELECTRIC DEVICE Filed Sept. 27, 1950 Fig.|.

Fig. 2.

S d 3| (0 E O. E 32 k C l I r L 3" II I 5 .9 g 2 30 ls l LIE-I 0' d o a Cathode Temperature WITNESSES: v INVENTOR 4034C Robert J. Bollard.

fi gamut I m ATTORN EY ,vide a cathode havin fla high emission -teristic per unit of surface-area.

Patented Sept. 22, 1953 VAPOR. ELECTRIC DEVICE LRobertLBallard, West Newton, Pa assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application asentc'mber 27, .0 er a -.1. ,1

"7 Claims. .1

My invention relates to a vapor electric device and particularly to asdevice-utilizing the vapors .of certain-alkali metals.

Since-the invention of a sealingmaterial which .will withstand the. chemical activity of :the alkali metals, it is now ,possibleto construct power type tubes utilizing the alkali metals ,sucha-s cesium,

rubidium and potassimn Ehaving an arc drop of .the order of 3.8 voltsand ran overallfefliciency of the order of'98%. gHoweven-certain drawbacks tothe commercial utilizationof these-devices are still apparent. .One of these is the size and.

weight of v the cathode necessary to produce a. de-

sirable current output. Fo-r-;examp1e, a'cathode capable of delivering a current of theorder of .l,0,00amperes would have a totalsurface area of the order of 350 square inches and a-total :weight, as now constructed, of -the order of 36 .pounds.

I have discovered that by-providinga cathode surface of substantially urenickel'with asmall ;.percentageof impurities: consisting essentially of .phosphides the? emission rate of v a cesium coated cathode can be increased-so that acathodeh ving an area of 35 0;square inches-isnowcapable-;of

can be considerably reduced. Forexamplethe (36 pound cathodeof-the prior-art can be reduced to substantially 32 poundsby utilizingmy invention.

' Heretofore, the best possible commercially available cathodes for cesium tubes were con- .structed of substantially pure nickel, but because ,of the mechanicalweakness of nickel, the size and shape ,of the. cathode has been materially circumscribed. :I-Iowever, lI-have found that the cathode can now beconstructed of suitable materials havingsuflicientstrengthsuch as steel, and the coating of nickel and nickel phosphide-aptplied to the-surface of the cathode and still produoe a-satisfactory emission device far 1 superior to the heretofore known nickel cathodes.

:It is accordingly an obj ects of my; invention to provide a cesium-vapor-electrio; devicehaving an ,increased currentcapacity.

.It i fu obiec of ;myz:. nv ntion:tonp ocharacv.It, is a fur r .Qbj-ect, of, my. invention to; pro- ,vide a. cathode, the .=acti ze..s,ur face of .which '2 composed of nickel with a small percentage of nickel .phosphide included.

Other objects and advantages of my invention will be apparentfrom the following detailed description taken .in conjunction with theacco npanying drawing, in which:

Figure 1 is an elevation partially in sec ig'n .of a vapor. electric device according to rny invention;

Fi 2 is a a mmatic illustrat on c the emission characteristics of nickel and nickel phosphide cathodes; and

Fig. 3 is anenlargedsection of apertiongfthe cathode of Fig. ,1.

In the exemplary embodiment. oflny invention, thevapor electric device comprises an anodeJ 0, preferably in the form of a cylindrical container having an opening at one end in which the cathode member 1,2 is inserted and sealed by -means of a glass-metal seal [3 resistant to the action of alkali metal vapor to provide a substantially closed-container. The cathode tubed tis'hollovv and contains a heating element-the terminals I6 1 of. which extend beyond the. cathode l.-2,, as. shown. "In' order to provide 'sufiicient cathode surface area, the cathode E552 .is provided with-a large number of extensions or fins l1 having. a. small space between the fins.

1 de pre e ex ss -transfer of hea from a cathode lz to the anode"), aheat shield I8 i no a y p ov ded ar un the ca ho .12 and ha port o ad c n t en arge i tfat area section H of the cathode lzis pmvidedwap op n s 9 io 'th ssa e of the e rqng'f om the cathode 1'2 tothe anode til. The anode-l9 itself is u u l o id d With. -11e :al2$m.bilinner ur 0tha ytli :h atwiiic isiqt ii P n o h an de'iifi rea i e -rb dee s t t rqo l wh ch MlQIIl EQY emulate in any desired,manner aropnd'the ontside of the anode ID.

A qua i o c sium.i ip acedinithe. containe to provide the actuating vapor and as is, knoy vn the cesium deposits in a probablynon-atomic layer on allofthe metal surfaces in the container.

.W ile the e act a t ni no urel known. it is known that the layerof cesium on a metal, u hoas cke W ic hasa .iun tiiinin ex ess of the ioni ionv pot n i o vapo produces a sur f appar n .lowworkiunctia n t a i r dil e t a.la eflowfl fe e tifen at a relatively low tdmpel'ttture. The irnpr-zoved .cathode coating according tothe presentinven- .tion LSQm tmann tllq filgl-fini l- 3 995 8??? electroplating in that oddshapes and deep recesses are equally well'plated with the smooth exterior surfaces.

I have found that nickel platring deposited by this process does indeed contain impurities, mostly in the form of phosphides,

particularly nickel phosphide. In a typical example of freshly deposited nickel plating, according to this process, it was found to contain substantially 93% pure nickel with approximately 7% of phosphides. Heat treating reduced the phosphide content to substantially 3%.

The improved cathode I2 is produced by constructing the basic body elements hi and ll of any metal having the desired mechanical properties and depositing by chemical reduction a nickel plate 2| on the active surface. As set forth the resultant plate or active surface 2% is composed of about 93% nickel and about 7% impurities mostly in the nature of p-hosphides. The plate 2| is heat treated at 1100 C. in a non-oxidizing atmosphere for about a half hour when the phosphides are found to be reduced to about 3% of the total plate.

The plate 21 can be deposited from either of the following baths:

Basic Acid Nickel Chloride 30-40 30-40 Sodium Hypophosphite 10-15 10-15 Ammonium Chloride. 50-60 Sodium Citrate 100-110 10-15 Ammonium hydroxide to pH of 8-10 Potassium hydroxide to pH of 4-6 Temperature .pH 0.. 90-95 90-95 nickel and phosphide coating 2 I, according to my process, had a total emission of 6.8 amperes per \square inch at a cathode temperature of 700 C. and an anode temperature or vapor pressure temperature of 180 C.

' The increase in emission at a lower tempera ture not only increases the current rating of the tube but materially decreases the operating difiiculties in the tube. Since the radiation from any heated surface is substantially at the fourth power of the temperature of the surface, the reduction from 780 C. to 700 C. has materially reduced the radiated energy and makes it much 7. easier to cool the anode or any control electrodes to a safe operating temperature.

Advantage of the. increased electron emission can be'takenby further reducing the vapor pressure, and consequently the cathode emission temperature. For example, if the vapor pressure temperature is dropped from 180 C. to C., as shown by curve 32, my improved cathode construction provides an emission of approximately 5.8 amperes per square inch at a cathode temperature of 660 0., or in other words, I have been able to get more than double the cathode emission from my improved cathode construction with a reduction of over 120 C. in the emitting surface.

The utilization of the chemically deposited coating 2! as the active cathode surface materially improves the possibilities as to cathode construction. For example, the cathode structure 52 may be made of steel or iron alloy which is easy to fabricate and has inherently great strength even when hot. Also the weight can be somewhat reduced as the density of the iron alloy is less than that of nickel which has heretofore been required.

The improved cathode of the present invention can be utilized either to increase the anode-cathode current per tube, or obviously if the current per tube is to remain constant, a great decrease in the size and weight of the tube will be immediately possible.

While I have shown a preferred embodiment of my invention and described the same according to the best of my present knowledge thereof, I desire it to be understood that such embodiment is exemplary only and that changes and modifications can be made Without departing from the spirit of my invention.

I claim as my invention:

1. A vapor electric valve comprising a container, a cathode in insulated relation to said container, a heater maintaining said cathode at emitting temperature, at least the emitting surface of said cathode consisting of nickel containing a small portion of nickel phosphide and a quantity of cesium providing a working vapor in said containerand cooperating with said emitting surface to produce high electron emission at low temperature of said surface.

2. A vapor electric valve comprising a container, a cathode in insulated relation to said container, a heater maintaining said cathode at emittingtemperature, at least the emitting surface of said cathode consisting of nickel containing 3 to 7 per cent of nickel phosphide and a working vapor in said container cooperating with said emitting surface to produce high electron emission at low temperature of said surface.

3. An electric discharge device comprising an anode, a cathode in spaced insulated relation to said anode, heating means maintaining said cathode at an electron emitting temperature, the surface of said cathode consisting of nickel containing impurities of the order of 3 to '7 per cent, said impurities being essentially nickel phosphide,

a quantity of cesium in said device, said cesium cooperating with said cathode surface to produce an emission of the order of 6.5 amperes per square inch of cathode surface at a cathode temperature of 700 C. and an anode temperature of 4:. In a hot-cathode vapor electric discharge device utilizing a metal vapor, selected from the group comprising cesium, rubidium and potassium, as the ionizable medium, a cathode comprising a metal body, at least one other electrode, and an enclosing housing, characterized 'by atleast the activeportion of said cathodebody having a surface-coating layer composed of nickel containing small quantities of phosphides, particularly nickel phosphide.

5. In a hotcathode vapor electric discharge device utilizing a metal vapor, selected from the group comprising cesium, rubidium and potassium, as the ionizable medium, a cathode comprising a metal body, at least one other electrode, and an enclosing housing, characterized by at least the active portion of said cathode-body having a surface-coating layer composed of nickel containing from 3 to 7 per cent of phosphides, particularly nickel phosphide.

6. In an electric discharge device having a heated cathode in the presence of cesium vapor,

a cathode body constructed of a ferrous metal alloy and an active surface coating layer composed of nickel containing a small percentage of phosphides, particularly nickel phosphide.

7. In an electric discharge device having a heated cathode in the presence of cesium vapor, a cathode body constructed of a ferrous metal alloy and an active surface coating layer composed of nickel containing 3 to 7 per cent of 10 phosphides, particularly nickel phosphide.

ROBERT J. BALLARD.

No references cited. 

